The present invention relates to a magnetic disc apparatus for storing information magnetically, or more in particular to a magnetic disc apparatus for reproducing information by use of the magneto-resistance effect.
A magneto-resistance effect film is generally used when reproducing information by use of the magneto-resistance effect. Conventional methods for eliminating the ferromagnetic domain wall which is formed within the magneto-resistance effect film are described below.
According to a method disclosed in U.S. Pat. No. 4,103,315, an antiferromagnetic film is formed over the entire surface of one side of a magneto-resistance effect film, and a magnetic coupling generated in the interface between the antiferromagnetic film and the magneto-resistance effect film (hereinafter referred to as "the magnetic exchange coupling") is used. An Fe--Mn alloy is most effective as the antiferromagnetic film, and may be replaced with nickel oxide or iron oxide with equal effect.
U.S. Pat. No. 4,663,685 (JP-A-62-40610), on the other hand, discloses a method in which a magnetic domain control layer configured of an antiferromagnetic material such as Fe--Mn alloy is formed at the upper ends of a magneto-resistance effect film, and the magnetic exchange coupling generated in the interface between the antiferromagnetic film and the magneto-resistance effect film is utilized.
Also, Journal of Applied Physics, Vol. 52, p. 2465, 1981, discloses the fact that the phenomenon of a reproduced signal distorted irregularly posing a problem in applying a magneto-resistance effect film to a reproduction magnetic head is caused by a ferromagnetic domain wall formed in the magneto-resistance effect film.
Further, JP-B-4-8848 discloses means for forming a single magnetic domain by applying a longitudinally biassing magnetic field to a magneto-resistance effect film.